(E)-N′-(2,4,6-Trihydroxy­benzyl­idene)isonicotinohydrazide sesquihydrate

In the title compound, C(13)H(11)N(3)O(4)·1.5H(2)O, the pyridine ring forms a dihedral angle of 1.50 (6)° with the benzene ring. An intra­molecular O—H⋯N hydrogen bond forms a six-membered ring with an S(6) ring motif. In the crystal structure, one water mol­ecule is disordered over two positions around an inversion centre with site-occupancy factors of 0.5. Inter­molecular O—H⋯N, O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds consolidate the structure into a three dimensional network. A π–π stacking inter­action with a centroid–centroid distance of 3.5949 (7) Å is also present.